The present invention pertains in general to optical devices usable for transmission of light signals in a communication network, and in particular to devices including self-contained means for maintaining a clean exterior surface.
The use of optical sensing devices is becoming increasingly popular for directly monitoring changes in physical parameters, such as those pertaining to environmental quality, and for monitoring the changes in physical mechanisms which in turn are responsive to variations in such parameters. This growing popularity is due in part to the extremely fine resolution attainable with optical devices, since movements of optical devices on the order of a fraction of an inch or of a degree can result in pronounced changes in the amounts of light reflected or transmitted by the device. For example, a light-reflecting mirror can be mechanically coupled to a mechanism which moves angularly in response to a change in temperature. If the mirror is used to reflect light from a fixed light source to a fixed light detector, and the intensity of the light received at the detector is indicative of the magnitude of the temperature, an angular movement of the mirror by a fraction of a degree can make an appreciable change in the amount of light intensity incident on the light detector. Therefore, minute changes in temperature, or some other physical parameter, can be discerned easily.
However, these optical sensing devices often are used in environments which tend to be particularly dirty. Air-borne or fluid-borne particles, to which the sensors may be continually subjected, eventually build up on the light-reflecting or light-transmitting surfaces and severely degrade the performance of the optical sensor. Cleaning the dirty surfaces, to restore the sensor to optimum efficiency, can be a costly, inconvenient process. If a sensor were located, for example, in a pipeline carrying a process fluid, removal of the device for cleaning purposes would necessitate shutdown of the fluid flow, meaning lost production and unnecessary cost.
Therefore, it is an object of the present invention to provide a self-cleaning optical device, which can periodically remove performance-degrading buildups of contaminants from its exterior light-interactive surfaces, so as to maintain optimum operating efficiency.